THIS invention relates to polycrystalline diamond compacts and more particularly to a method of manufacturing polycrystalline diamond compacts.
A commonly used cutting tool insert for drill bits is one which comprises a layer of polycrystalline diamond (PCD) bonded to a cemented carbide substrate. The layer of PCD presents a working face and a cutting edge around a portion of the periphery of the working surface. Polycrystalline diamond comprises a mass of diamond particles containing a substantial amount of direct diamond-to-diamond bonding.
U.S. Pat. No. 4,224,380 discloses a compact consisting essentially of self-bonded abrasive particles with an interconnected network of pores dispersed throughout. The compact is produced by bonding a mass of abrasive particles into a self-bonded body through the use of a sintering aid material under high pressures and temperatures (HP/HT). The body formed at HP/HT includes the self-bonded particles with the sintering aid material (e.g., cobalt or cobalt alloys) infiltrated throughout the body. The infiltrant is then removed, for example, by immersion of the body in an aqua regia bath. It has been discovered that the removal of substantially all of the infiltrant provides an abrasive particles compact which has substantially improved resistance to thermal degradation at high temperatures.
U.S. Pat. No. 4,944,772 discloses a process for fabricating a supported polycrystalline diamond or CBN compact in general, though such process is especially adapted to the fabrication of a thermally-supported polycrystalline diamond or CBN compact. The process comprises forming a sintered polycrystalline diamond or CBN compact having a surface and separately forming a cemented carbide support having a support surface. The compact and support then are mated at their respective surfaces with a layer of diamond or CBN crystals having the largest dimension of between about 30 and 500 micrometers interposed between said surfaces. Also, a source of diamond or CBN catalyst/sintering aid material is associated with the layer of diamond or CBN crystals. The mated compact and support then are subjected to HP/HT conditions and for a time adequate for converting said diamond or CBN crystals into a polycrystalline diamond or CBN compact and for producing a supported polycrystalline compact of at least two polycrystalline layers (i.e. bi-layer compact). Preferably, thermally-stable compacts are used in the process.
U.S. Pat. No. 5,127,923 discloses a highly consolidated abrasive compact which has enhanced particle-to-particle bonding, increased density and improved thermal stability performance characteristics and which can be bonded directly to a supporting substrate. The compact is produced by subjecting a mass of abrasive particles, e.g., diamond or cubic born nitride, to multiple pressure cycles at high temperatures. A solvent-catalyst sintering aid is employed in the initial pressure cycle. The compact then possesses residual interconnected porosity in the particle mass which is filled with the solvent-catalyst. Depending upon the degree of sintering, the solvent-catalyst can be removed by leaching or other suitable process. The removal of the solvent-catalyst permits further consolidation and sintering of the particle mass in subsequent pressure cycles. During the final pressure cycle, the abrasive mass can be bonded to a supporting substrate. In addition, a non-catalyst sintering aid, such as silicon, boron or metals rendered non-catalytic by the addition of silicon or boron which may form strong and chemically-resistant carbides, can be used in the second pressure cycle to enhance the sintering process and create a hard abrasive bonding matrix through out the particle mass.
Japan patent publication number JP 59219500 discloses chemical treatment of a working surface of a PCD element. This treatment dissolves and removes the catalyst/solvent matrix in an area immediately adjacent to the working surface. The invention is claimed to increase the thermal resistance of the PCD material in the region where the matrix has been removed without compromising the strength of the sintered diamond.
U.S. Pat. Nos. 6,544,308 and 6,562,462 disclose a PCD element having a body with a working surface. A first volume of the body remote from the working surface contains a catalyzing material, and a second volume of the body adjacent to the working surface is substantially free of the catalyzing material.
There is a need for polycrystalline diamond compacts having excellent thermal stability in use combined with high strength and fracture resistance, and a cost-effective method for making them.